Key Physics of the Madden-Julian Oscillation Based on Multi-model Simulations

Transcription

1 Key Physics of the Madden-Julian Oscillation Based on Multi-model Simulations Xianan Jiang Joint Institute for Regional Earth System Sci. & Engineering / Univ. of California, Los Angeles Jet Propulsion Laboratory / California Institute of Technology, Pasadena Acknowledgments: Eric Maloney (CSU), Ming Zhao (GFDL), Duane Waliser (JPL), Alex Gonzalez (UCLA), Prince Xavier, Jon Petch (UKMO), Nick Klingaman, Steve Woolnough (U. Reading) 1

2 Vertical Structure and Diabatic Processes of the MJO: Global Model Evaluation Project MJO Task Force/YOTC and GASS Model Experiment Science Focus Exp. POC I. 20 Yr Climatological Simulations ( if AGCM) 6-hr, Global Output Vertical Structure, Physical Tendencies Model MJO Fidelity Vertical structure Multi-scale Interactions: (e.g., TCs, Monsoon, ENSO) UCLA/JPL X. Jiang D. Waliser Jiang et al (2015) II. 2-Day MJO Hindcasts YOTC MJO Cases E & F (winter 2009) Time Step, Indo-Pacific Domain Output Very Detailed Physical/Model Processes Heat and moisture budgets Model Physics Evaluation (e.g. Convection/Cloud/BL) Short range Degradation Met Office P. Xavier J. Petch Xavier et al (2015) III. 20-Day MJO Hindcasts YOTC MJO Cases E & F (winter 2009) 3-hr, Global Output Elements of I & II MJO Forecast Skill State Evolution/Degradation Elements of I & II NCAS/Walker in. N. Klingaman S. Woolnough Klingaman et al (2015a,b) Commitments: About 30 Modeling Groups with AGCM and/or CGCM 2

3 Amplitude of Winter MJO in Multi-model Simulations Vertical Structure and Diabatic Processes of the MJO: Global Model Evaluation Project MJO Task Force/YOTC and GASS MJO Amplitude day Rain STD during winter (Nov-Apr) Indo-Pacific Pool ( o E; 15 S-15 N) Jiang et al

4 Vertical Structure and Diabatic Processes of the MJO: Global Model Evaluation Project MJO Task Force/YOTC and GASS MJO Fidelity MJO Propagation Simulated in GCMs Lag-regression of rainfall to Indian Ocean base point (70-90 o E; 5 o S-5 o N) day filtered dash line 5 m/s Jiang et al

5 Skill for MJO Propagation based on Rainfall Hovmöller Diagram Top 25% models Bottom 25% models GISS_ModelE2 SPCCSM SPCAM MRI_AGCM PNU_CFS CNRM_CM NCHU_ECHAM5 TAMU_modCAM4 OBS Good MJO models Poor MJO models Jiang et al

6 MJO Process-oriented Diagnosis Based on MSE budget Moist Static Energy (MSE): m = C G T + gz + Lq Moisture Mode theory for MJO Neelin and Yu (1994); Raymond and Fuchs (2008); Raymond et al. (2009); Sobel and Maloney (2012, 13) MJO physics is governed by feedbacks that regulate moisture anomalies!"!# = '()" * +, +- + LE + SH + LW + SW F MNOP Circulation (GMS) Wind-evaporation Radiation Q R Raymond & Fuchs (2008) Chikira (2014) Pritchard & Bretherton (2014) Benedict et al (2014) Maloney et al. (2014) Neelin et al. (1987) Maloney & Sobel (2004) Sobelet al. (2008) Maloney (2010) Kiranmayi & Maloney (2011) Raymond (2001) Bony & Emanuel (2005) Andersen & Kuang (2012) 6

7 !"!# = '()" * +, +- + F MNOP + Q R 22 levels hPa Regressed to d rainfall (scaled to 3 mm d -1 ) over Indian Ocean (75-85 o E; 5 o S-5 o N) Rainfall MSE OBS Good GCMs Poor GCMs 7

8 OBS Good GCMs Poor GCMs rainfall mm/day m m t Scaled by 3 mm d -1 over Indian Ocean (75-85 o E; 5 o S-5 o N) Jiang et al. 2016a MJO Propagation skill MSE tendency pattern skill 8

9 I. Factors regulating MJO amplitude!"!# = '()" * +, +- + F MNOP + Q R Projection OBS MSE m amplifying damping MSE sources MSE sinks OBS m t ')(" *!"!X Q R F surf 9

10 MJO Amplitude vs MSE source/sink MJO amplitude vs MSE export Corr=-0.68 MJO amplitude vs MSE input Corr=-0.82 Corr=-0.81 MJO Amplitude MJO Amplitude Total MSE Export ')(" + *!"!X F surface + Q R ~ NGMS Reduced MSE Export Strong MJO Benedict et al (2014); Maloney et al. (2014) Radiative Instability?? Raymond (2001) Andersen & Kuang (2012) Jiang et al. 2016a 10

11 MJO Amplitude vs Precipitable Water!"!# = '()" * +, +- + Q R + F MNOP m = C G T + gz + Lq MJO Amplitude Corr=-0.76 τ c = Wb P b Convective Adjustment Time-scale Brethertonet al. (2004) Raymond et al (2007) Sobel and Maloney (2012,13) Adams and Kim (2016) Precipitable Water (W ~ <q>) Jiang et al. 2016b 11

12 MJO Amplitude and the Convective Time Scale τ c = Wb Bretherton et al. (2004), Convective Adjustment Time-scale: P b Holloway and Neelin (2009) τ c Models Jiang et al. 2016a 12

13 Composite W vs P in GCMs with long/short τ c W & P : day filtered. Composite over tropical Indian Ocean (60-90E;10S-10N) Jiang et al. 2016a 13

14 MJO vertical structure in GCMs with long/short τ c 14

15 II. Model processes regulating MJO propagation!"!# = '()" * +, +- + F MNOP + Q R Projection OBS MSE Tendency!"!# Eastward Westward 15

16 !"!# Role of horizontal MSE advection for MJO Propagation!"!# = '()" * +, +- + Q R + F MNOP MSE budget analysis by projection onto!"!# def OBS Good GCMs Poor GCMs Jiang et al. 2016b m t '()" *!"!X Q R F surf 16

17 Temporal-scale decomposition of horizontal MSE transport OBS '()" ' v ()"w ' vv ()" vv Total zonal meridional For both v and m A = A + A b + A A : > 100 d A b : d A bb : < 20 d Good GCMs Poor GCMs Maloney (2009) Andersen and Kuang (2012) Total -> Jiang et al. 2016b 17

18 Why ' v ()"w is not well simulated in Poor MJO models? ERA-Interim 700hPa Shading: mean MSE (mw) Vector: MJO winds (v b ) J/(Kg.K) Good GCMs Poor GCMs Biases in both mw and ' v! Jiang et al. 2016b 18

19 Dry air intrusion associated with the MJO During the DYNAMO Kerns and Chen (2014) 19

20 III. A Diagnostic Metric for Model MJO Eastward Propagation Winter mean hPa specific humidity 0.62 cor= Gonzalez and Jiang

21 MJO Propagation skill Cor=0.79 Gonzalez and Jiang 2016 Winter mean hPa specific humidity 21

22 Summary An adjustment time scale for convection in responding to a departure from the quasi-equilibrium state in the atmospheric moisture is found to be closely linked to the model MJO amplitude; Horizontal MSE transport, with primary contribution by the lower-tropospheric mean MSE by MJO circulations, plays a critical role for realistic eastward propagation of the MJO in good MJO models; Model fidelity in seasonal mean low-level tropospheric moisture pattern over the Maritime continent and western equatorial Indian Ocean are highly correlated to model MJO propagation skill, thus can serve as good diagnostic metrics for model skill in representing the eastward propagation of the MJO. 22

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24 Vertical MJO Structures in Good and Poor Models w (Pa/s) Q (k/day) q (g/kg) ERA-Interim Good GCMs Poor GCMs (10 o S-10 o N) Jiang et al